Phase 1 investigation of lenalidomide/rituximab plus outcomes of lenalidomide maintenance in relapsed CNS lymphoma.

There is an unmet need for effective biological therapies for relapsed central nervous system (CNS) lymphoma. Lenalidomide is active in activated B-cell type diffuse large B-cell lymphoma and rituximab is effective in CNS lymphoma. These observations are the basis for this first trial of an immunomodulatory drug as monotherapy in CNS lymphoma, and, in patients with inadequate responses to lenalidomide, with rituximab. In an independent cohort, we evaluated lenalidomide maintenance after salvage with high-dose methotrexate or focal irradiation in relapsed primary CNS lymphoma (PCNSL). We determined safety, efficacy, and cerebrospinal fluid (CSF) penetration of lenalidomide at 10-, 15-, and 20-mg dose levels in 14 patients with refractory CD20+ CNS lymphoma. Nine subjects with relapsed, refractory CNS lymphoma achieved better than partial response with lenalidomide monotherapy, 6 maintained response ≥9 months, and 4 maintained response ≥18 months. Median progression-free survival for lenalidomide/rituximab was 6 months. In the independent cohort, response duration with lenalidomide maintenance after complete responses 2 through 5 were significantly longer than response durations after standard therapy. The CSF/plasma partition coefficient of lenalidomide was ≥20% at 15- and 20-mg dose levels. Change in CSF interleukin-10 at 1 month correlated with clinical response and response duration to lenalidomide. Metabolomic profiling of CSF identified novel biomarkers, including lactate, and implicated indoleamine-2,3 dioxygenase activity with CNS lymphoma progression on lenalidomide. We conclude that lenalidomide penetrates ventricular CSF and is active as monotherapy in relapsed CNS lymphomas. We provide evidence that maintenance lenalidomide potentiates response duration after salvage in relapsed PCNSL and delays whole brain radiotherapy (WBRT). This trial was registered at www.clinicaltrials.gov as #NCT01542918.

Long-term survival in AIDS-related primary central nervous system lymphoma.

BACKGROUND: The optimal therapeutic approach for patients with AIDS-related primary central nervous system lymphoma (AR-PCNSL) remains undefined. While its incidence declined substantially with combination antiretroviral therapy (cART), AR-PCNSL remains a highly aggressive neoplasm for which whole brain radiotherapy (WBRT) is considered a standard first-line intervention. METHODS: To identify therapy-related factors associated with favorable survival, we first retrospectively analyzed outcomes of AR-PCNSL patients treated at San Francisco General Hospital, a public hospital with a long history of dedicated care for patients with HIV and AIDS-related malignancies. Results were validated in a retrospective, multicenter analysis that evaluated all newly diagnosed patients with AR-PCNSL treated with cART plus high-dose methotrexate (HD-MTX). RESULTS: We provide evidence that CD4+ reconstitution with cART administered during HD-MTX correlates with long-term survival among patients with CD4 <100. This was confirmed in a multicenter analysis which demonstrated that integration of cART regimens with HD-MTX was generally well tolerated and resulted in longer progression-free survival than other treatments. No profound differences in immunophenotype were identified in an analysis of AR-PCNSL tumors that arose in the pre- versus post-cART eras. However, we detected evidence for a demographic shift, as the proportion of minority patients with AR-PCNSL increased since advent of cART. CONCLUSION: Long-term disease-free survival can be achieved in AR-PCNSL, even among those with histories of opportunistic infections, limited access to health care, and medical non-adherence. Given this, as well as the long-term toxicities of WBRT, we recommend that integration of cART plus first-line HD-MTX be considered for all patients with AR-PCNSL.

CNS intravascular large cell lymphoma in a patient with autoimmune hemolytic anemia.

Intravascular large cell lymphoma (IVLCL) is a rare disease characterized by proliferation of malignant lymphocytes within the small blood vessel lumens. The association of IVLCL with autoimmune hemolytic anemia (AIHA) has been described in a single case report, but the true prevalence of this co-occurrence is not known because of declining autopsy rates. Here, we report a case of a 41-year-old woman who carried a diagnosis of AIHA for 2 years, with repeated hemolytic episodes that were initially well controlled with immunomodulatory treatment. At her last presentation, the patient developed rapidly progressive neurologic symptoms and leukoencephalopathy on MRI; she died 4 weeks later with a clinical impression of thrombotic microangiopathy, a known complication of AIHA. At autopsy, the brain showed widespread platelet thrombi and intraparenchymal hemorrhages characteristic of this disorder. In addition, there was evidence of a clinically unsuspected IVLCL, most likely of B-cell lineage. This case illustrates a potential association between IVLCL and AIHA, highlights the need for broad differential diagnosis in cases with atypical disease presentation or progression, and underlines the importance of autopsy in establishing the full cause of morbidity and mortality.

Vasal injury during inguinal herniorrhaphy: a case report and review of the literature.

An injury to the vas deferens during inguinal herniorrhaphy from possible tethering of the vas has not, to our knowledge, previously been described in the surgical literature. We report a case of iatrogenic injury of the vas deferens that occurred during elective hernia repair in a 28-year-old man who had previously sustained blunt trauma to the abdomen and pelvis.

How I treat CNS lymphomas.

The pathogenesis of primary and secondary central nervous system (CNS) lymphoma poses a unique set of diagnostic, prognostic, and therapeutic challenges. During the past 10 years, there has been significant progress in the elucidation of the molecular properties of CNS lymphomas and their microenvironment, as well as evolution in the development of novel treatment strategies. Although a CNS lymphoma diagnosis was once assumed to be uniformly associated with a dismal prognosis, it is now reasonable to anticipate long-term survival, and possibly a cure, for a significant fraction of CNS lymphoma patients. The pathogenesis of CNS lymphomas affects multiple compartments within the neuroaxis, and proper treatment of the CNS lymphoma patient requires a multidisciplinary team with expertise not only in hematology/oncology but also in neurology, neuroradiology, neurosurgery, clinical neuropsychology, ophthalmology, pathology, and radiation oncology. Given the evolving principles of management and the evidence for improvements in survival, our goal is to provide an overview of current knowledge regarding the pathogenesis of CNS lymphomas and to highlight promising strategies that we believe to be most effective in establishing diagnosis, staging, and therapeutic management.

CXCL13 plus interleukin 10 is highly specific for the diagnosis of CNS lymphoma.

Establishing the diagnosis of focal brain lesions in patients with unexplained neurologic symptoms represents a challenge. The goal of this study is to provide evidence supporting functional roles for CXC chemokine ligand (CXCL)13 and interleukin (IL)-10 in central nervous system (CNS) lymphomas and to evaluate the utility of each as prognostic and diagnostic biomarkers. We demonstrate for the first time that elevated CXCL13 concentration in cerebrospinal fluid (CSF) is prognostic and that CXCL13 and CXCL12 mediate chemotaxis of lymphoma cells isolated from CNS lymphoma lesions. Expression of the activated form of Janus kinase 1 supported a role for IL-10 in prosurvival signaling. We determined the concentration of CXCL13 and IL-10 in CSF of CNS lymphoma patients and control cohorts including inflammatory and degenerative neurologic disease in a multicenter study involving 220 patients. Bivariate elevated CXCL13 plus IL-10 was 99.3% specific for primary and secondary CNS lymphoma, with sensitivity significantly greater than reference standard CSF tests. These results identify CXCL13 and IL-10 as potentially important biomarkers of CNS lymphoma that merit further evaluation and support incorporation of CXCL13 and IL-10 into diagnostic algorithms for the workup of focal brain lesions in which lymphoma is a consideration.

Use of an expanded immunohistochemical panel to distinguish cutaneous Hodgkin lymphoma from histopathologic imitators.

In lymph nodes, classical Hodgkin lymphoma can typically be distinguished from non-Hodgkin lymphoma (NHL) by the presence of Hodgkin and Reed-Sternberg cells that co-express CD30 and CD15. However, anaplastic large cell lymphoma (ALCL) and diffuse large B-cell lymphoma (DLBCL) can show identical features, and some cases of classical Hodgkin lymphoma lack CD15 expression, rendering them difficult to differentiate from CD30-positive NHL. The differential diagnosis of cutaneous Hodgkin lymphoma similarly includes ALCL and DLBCL, and, additionally, tumors of mycosis fungoides. Recent studies have shown that classical Hodgkin lymphoma is of B-cell origin in virtually all cases, and shows at least focal weak expression of the B-cell marker PAX5 and often focal weak expression and no expression of the B-cell markers Oct-2 and BOB.1, respectively. All three of these markers are almost invariably absent in T-cell lymphomas and are strongly expressed in B-cell lymphomas. We report a 40-year-old man with classical Hodgkin lymphoma who developed cutaneous nodules. A biopsy from one revealed Hodgkin/Reed-Sternberg cells with a similar immunophenotype to the diagnostic lymph node biopsy, namely CD30+/CD15+, diffusely but weakly PAX5+, focally weakly Oct-2+ and lacking BOB.1 expression, thereby confirming a diagnosis of cutaneous Hodgkin lymphoma. To our knowledge, this is the first report of the expression pattern of the combination of PAX5, Oct-2 and BOB.1 in the context of cutaneous involvement by Hodgkin lymphoma.

Immunochemotherapy with intensive consolidation for primary CNS lymphoma: a pilot study and prognostic assessment by diffusion-weighted MRI.

PURPOSE: We evaluated a novel therapy for primary central nervous system lymphoma (PCNSL) with induction immunochemotherapy with high-dose methotrexate, temozolomide, and rituximab (MT-R) followed by intensive consolidation with infusional etoposide and high-dose cytarabine (EA). In addition, we evaluated the prognostic value of the minimum apparent diffusion coefficient (ADC(min)) derived from diffusion-weighted MRI (DW-MRI) in patients treated with this regimen. EXPERIMENTAL DESIGN: Thirty-one patients (median age, 61 years; median Karnofsky performance score, 60) received induction with methotrexate every 14 days for 8 planned cycles. Rituximab was administered the first 6 cycles and temozolomide administered on odd-numbered cycles. Patients with responsive or stable central nervous system (CNS) disease received EA consolidation. Pretreatment DW-MRI was used to calculate the ADC(min) of contrast-enhancing lesions. RESULTS: The complete response rate for MT-R induction was 52%. At a median follow-up of 79 months, the 2-year progression-free and overall survival were 45% and 58%, respectively. For patients receiving EA consolidation, the 2-year progression-free and overall survival were 78% and 93%, respectively. EA consolidation was also effective in an additional 3 patients who presented with synchronous CNS and systemic lymphoma. Tumor ADC(min) less than 384 × 10(-6) mm(2)/s was significantly associated with shorter progression-free and overall survival. CONCLUSIONS: MT-R induction was effective and well tolerated. MT-R followed by EA consolidation yielded progression-free and overall survival outcomes comparable to regimens with chemotherapy followed by whole-brain radiotherapy consolidation but without evidence of neurotoxicity. Tumor ADC(min) derived from DW-MRI provided better prognostic information for PCNSL patients treated with the MTR-EA regimen than established clinical risk scores.

In-transit intramammary sentinel lymph nodes from malignant melanoma of the trunk.

OBJECTIVE: Our goal was to determine the incidence and outcomes of intramammary in-transit sentinel lymph nodes (IMSLN) from primary malignant melanoma (MM) of the trunk. We hypothesize that regional metastasis to the breast from anterior trunk MM also occurs via the lymphatic system to these intramammary in-transit sentinel lymph nodes. BACKGROUND: MM is the most common solid tumor metastasis to the breast. The mechanism of intramammary (IM) metastasis is generally attributed to hematogenous rather than lymphatic spread. METHODS: We retrospectively reviewed medical records from all patients who underwent selective sentinel lymph node dissection at the UCSF Melanoma Center from 1993 to 2008 after the approval of UCSF Committee on Human Research. Of the 1911 cases, we found 614 patients with primary MM located on the trunk, and queried their medical records for in-transit SLN and SLNs in the breast. Data from preoperative lymphoscintigraphy, intraoperative lymphatic mapping, operative notes, and pathology and clinic notes were gathered. RESULTS: Of the 1911 patients with MM, 169 (8.9%) and 420 (22.0%) had anterior and posterior trunk lesions, respectively, and 25 patients (1.3%) with flank lesions (lateral abdominal wall below the rib cage, above the iliac crest). Of the anterior trunk population, 18 patients had in-transit SLNs. The vast majority of these patients (14 of 18, 77.8%) had in-transit IMSLN. Of patients with posterior trunk melanoma, 27 patients had in-transit nodes with 1 patient having IMSLNs. Of patients with flank melanomas, 3 patients had in-transit nodes with 1 patient having IMSLNs. Interestingly, all patients with IMSLNs had primary lesions located inferior to the breasts. Two of the 16 patients with IMSLNs had micrometastasis to IMSLN; 1 patient died and the other currently is disease free 4 years after initial SLND. Four of the 32 patients with non-IM in-transit nodes had micrometastases to these in-transit nodes. Of all patients with trunk melanomas, 4 patients had micrometastases to axillary SLNs (AxSLNs). Three of the 4 patients with positive AxSLNs also had positive in-transit nodes whereas only half of the patients with positive in-transit SLNs had positive AxSLNs. CONCLUSIONS: IMSLNs exist in the breast. Our results establish an anatomic basis for lymphatic metastasis to the breast from primary cutaneous melanoma mainly from the anterior trunk inferior to the breasts. For anterior trunk melanomas, IMSLNs should not be overlooked during SLND as they may harbor micrometastasis.

Atraumatic splenic rupture: an unusual manifestation of acute HIV infection.

A 27-year-old white male, who had sex with other men, presented to the emergency department with 3 days of left shoulder and abdominal pain. He reported no history of trauma to the abdomen. On abdominal imaging, he was found to have hemoperitoneum from a ruptured spleen; he underwent splenectomy. Causes of atraumatic splenic rupture can be divided into six main categories: infectious, neoplastic, inflammatory, congenital or structural, iatrogenic, and idiopathic. Work-up of the atraumatic splenic rupture revealed that his HIV antibody was newly positive. He had a documented negative HIV antibody 3 weeks prior to the current admission. CD4 cell count, obtained after splenectomy, was 904 cells per microliter and the HIV-1 plasma RNA level was 4657 copies per milliliter. Spleen pathology demonstrated an enlarged spleen with increase in the number of small to intermediate size lymphoid cells in the red pulp, and reactive follicular lymphoid hyperplasia, with numerous secondary lymphoid follicles and reactive germinal centers in the white pulp. T-cell receptor (TCR) gene rearrangement studies demonstrated a positive TCR beta gene rearrangement, without a TCR gamma gene rearrangement, consistent with a clonal CD8(+) T-cell population. The case gives rare insight into what happens in the spleen during acute HIV infection and encourages HIV testing in those presenting with atraumatic splenic rupture. Counseling patients with acute HIV to avoid potential trauma should also be considered.

Selective sentinel lymph node dissection for melanoma: importance of harvesting nodes with lower radioactive counts without the need for blue dye.

BACKGROUND: Determining how many sentinel lymph nodes (SLNs) should be removed for melanoma is important. The purpose of this study is to determine the frequency at which nodes that are less radioactive than the "hottest" node (which is negative) are positive for melanoma, how low of a radioactivity should warrant harvest, and if isosulfan blue is necessary. METHODS: We reviewed 1,152 melanoma patients who underwent lymphoscintigraphy with technetium, with or without blue dye, and SLN dissection from 1996 to 2008. SLNs with radioactivity ≥10% of the "hottest" SLN, all blue nodes, and all suspicious nodes were removed and analyzed. The miss rate was calculated as the proportion of node positive cases in which the "hottest" SLN was negative. RESULTS: SLNs were identified in 1,520 nodal basins in 1,152 patients. SLN micrometastases were detected in 218 basins (14%) in 204 patients (18%). In 16% of SLN-positive patients (33/204 patients), the positive SLN was found to have a lower radioactive count than the "hottest" SLN, which was negative. In 21 of these cases, the positive SLNs had radioactivity ≤50% of the "hottest" SLN. The 10% rule significantly reduced the miss rate to 2.5% compared with removal of only the "hottest" SLN (miss rate = 16%). Also, blue dye did not significantly decrease the miss rate compared with radiocolloid alone using the 10% rule. CONCLUSIONS: To decrease the miss rate, all SLNs with ≥10% of the ex vivo radioactivity of the "hottest" SLN should be removed and blue dye is not essential.

Intraoperative frozen section analysis of sentinel lymph nodes in breast cancer patients: a meta-analysis and single-institution experience.

BACKGROUND: Accurate intraoperative pathologic examination of sentinel lymph nodes (SLNs) has been an important tool that can reduce the need for reoperations in patients with SLN-positive breast cancer. The objective of the current study was to determine the accuracy of intraoperative frozen section (IFS) of SLNs during breast cancer surgery. METHODS: The authors retrospectively reviewed the records of 326 patients with breast cancer who underwent IF analysis of SLNs at a single institution. Then, they conducted a meta-analysis that included 47 published studies of IFS of SLNs in patients with breast cancer. RESULTS: Hematoxylin and eosin (H&E) staining revealed metastasis in SLNs in 99 patients (30.4%), including 61 patients with macrometastasis (MAM) (>2 mm) (the MAM group) and 38 patients with micrometastasis (Mi) or isolated tumor cell (ITC) deposits (the Mi/ITC group). The overall sensitivity of the institutional series was 60.6% (60 of 99 patients), and overall specificity was 100% (227 of 227 true negatives). The sensitivity of IFS was significantly lower in the Mi/ITC group (28.9%) than in the MAM group (80.3%; P < .0001). According to the meta-analysis of published studies and data from the author's institution (47 studies, for a total of 13,062 patients who underwent SLN dissection with IFS of SLNs), the mean sensitivity was 73%, and the mean specificity was 100%. The mean sensitivity was 94% for the MAM group and 40% for the Mi/ITC group. CONCLUSIONS: IFS of SLNs was more reliable for detecting MAM than for detecting Mi/ITC deposits. It lacked sufficient accuracy to rule out Mi/ITC deposits.

Prognostic implications of positive nonsentinel lymph nodes removed during selective sentinel lymphadenectomy for breast cancer.

Nonsentinel lymph nodes (SLNs) are commonly removed at the time of selective sentinel lymphadenectomy (SSL). Their predictive value for the rest of the nodal basin is unknown. A retrospective review of 436 breast cancer patients who underwent SSL between 12/97 and 04/03 at a single institution. One-hundred nineteen patients had non-SLNs removed at SSL; eight were positive (6.7%). Positive non-SLNs predicted that SLNs would also be positive (p = 0.008). There was no difference in rates of additional positive nodes found on completion axillary node dissection between the non-SLN and SLN positive patients (p = 0.62). After adjustment for covariates, the presence of positive non-SLNs was not associated with poorer disease free survival (p = 0.24), time to systemic recurrence (p = 0.57), or overall survival (p = 0.70). Positive non-SLNs removed during SSL are not a significant risk factor for additional positive nodes on completion axillary nodal dissection (CALND) or for worse survival than positive SLNs.

Pathologic correlates of primary central nervous system lymphoma defined in an orthotopic xenograft model.

PURPOSE: The prospect for advances in the treatment of patients with primary central nervous system lymphoma (PCNSL) is likely dependent on the systematic evaluation of its pathobiology. Animal models of PCNSL are needed to facilitate the analysis of its molecular pathogenesis and for the efficient evaluation of novel therapeutics. EXPERIMENTAL DESIGN: We characterized the molecular pathology of CNS lymphoma tumors generated by the intracerebral implantation of Raji B lymphoma cells in athymic mice. Lymphoma cells were modified for bioluminescence imaging to facilitate monitoring of tumor growth and response to therapy. In parallel, we identified molecular features of lymphoma xenograft histopathology that are evident in human PCNSL specimens. RESULTS: Intracerebral Raji tumors were determined to faithfully reflect the molecular pathogenesis of PCNSL, including the predominant immunophenotypic state of differentiation of lymphoma cells and their reactive microenvironment. We show the expression of interleukin-4 by Raji and other B lymphoma cell lines in vitro and by Raji tumors in vivo and provide evidence for a role of this cytokine in the M2 polarization of lymphoma macrophages both in the murine model and in diagnostic specimens of human PCNSL. CONCLUSION: Intracerebral implantation of Raji cells results in a reproducible and invasive xenograft model, which recapitulates the histopathology and molecular features of PCNSL, and is suitable for preclinical testing of novel agents. We also show for the first time the feasibility and accuracy of tumor bioluminescence in the monitoring of a highly infiltrative brain tumor.

Is it necessary to harvest additional lymph nodes after resection of the most radioactive sentinel lymph node in breast cancer?

BACKGROUND: No consensus exists about the number of sentinel lymph nodes (SLNs) that should be removed based on radioactivity counts in breast cancer, although the "10% rule" is often used. We hypothesized that the node with the highest radioactivity would have the strongest probability of being a positive SLN, and we sought to determine the lowest radioactive count of a node harboring cancer. STUDY DESIGN: We retrospectively studied 332 breast cancer patients who underwent lymphoscintigraphy by injection of technetium 99m-labeled thiosulfate colloid and sentinel lymphadenectomy (SL) between 1997 and 2006, with intraoperative determination of radioactive counts of nodes by a gamma probe. All SLNs were examined by permanent sections consisting of at least 3 levels of 40- to 100-mum intervals for hematoxylin and eosin evaluation, with or without immunohistochemical staining for cytokeratins. RESULTS: Seventy-four percent of patients had more than 1 SLN removed (mean 2.8 per patient); 23.5% had SLN metastasis. Of the node-positive patients, the hottest SLN was positive in 85.9% (67 of 78). Five of the 78 patients (6.4%) with positive nodes had counts less than 10% of those of the hottest node. The lowest radioactive count of a positive SLN was 4.2% of that of the hottest node. Lymphatic mapping based on the 10% rule could greatly improve the false-negative rates compared with removing only the hottest SLN (14.1% versus 6.4%). CONCLUSIONS: Most positive SLNs had the highest radioactivity. Our institutional experience indicates that to obtain an acceptable false-negative rate, nodes should be removed until the 10% rule is met.

Protein biomarker identification in the CSF of patients with CNS lymphoma.

PURPOSE: Elucidation of the CSF proteome may yield insights into the pathogenesis of CNS disease. We tested the hypothesis that individual CSF proteins distinguish CNS lymphoma from benign focal brain lesions. METHODS: We used a liquid chromatography/mass spectrometry-based method to differentially quantify and identify several hundred CSF proteins in CNS lymphoma and control patients. We used enzyme-linked immunosorbent assay (ELISA) to confirm one of these markers in an additional validation set of 101 cases. RESULTS: Approximately 80 CSF proteins were identified and found to be present at significantly different concentrations, both higher and lower, in training and test studies, which were highly concordant. To further validate these observations, we defined in detail the expression of one of these candidate biomarkers, antithrombin III (ATIII). ATIII RNA transcripts were identified within CNS lymphomas, and ATIII protein was localized selectively to tumor neovasculature. Determination of ATIII concentration by ELISA was significantly more accurate (> 75% sensitivity; > 98% specificity) than cytology in the identification of cancer. Measurement of CSF ATIII levels was found to potentially enhance the ability to diagnose and predict outcome. CONCLUSION: Our findings demonstrate for the first time that proteomic analysis of CSF yields individual biomarkers with greater sensitivity in the identification of cancer than does CSF cytology. We propose that the discovery of CSF protein biomarkers will facilitate early and noninvasive diagnosis in patients with lesions not amenable to brain biopsy, as well as provide improved surrogates of prognosis and treatment response in CNS lymphoma and brain metastasis.

Rare oral cavity presentation of a B-cell lymphoblastic lymphoma. A case report and review of the literature.

Lymphoblastic lymphoma is an uncommon malignancy, with most cases showing a T-cell phenotype and presenting as a mediastinal mass. By contrast, B-cell lymphoblastic lymphoma/leukemia is a rare high-grade malignancy that comprises approximately 10% of all lymphoblastic lymphomas. Lymphomas of the oral cavity are rare and typically present as intraosseous lesions that are most commonly diffuse large B-cell type. Here we present what we believe is the first B-cell lymphoblastic lymphoma initially presenting in the oral cavity. The case involves a 46-year-old white woman who presented with a mass in the right mandible. This report discusses this rare malignancy, including clinical presentation, histopathologic features, immunologic profile, treatment, and prognosis. This case emphasizes the importance of recognizing rare entities that may present in the oral cavity and the impact of the disease and its management.

Proposed classification of lymphoid neoplasms for epidemiologic research from the Pathology Working Group of the International Lymphoma Epidemiology Consortium (InterLymph).

Recent evidence suggests that there is etiologic heterogeneity among the various subtypes of lymphoid neoplasms. However, epidemiologic analyses by disease subtype have proven challenging due to the numerous clinical and pathologic schemes used to classify lymphomas and lymphoid leukemias over the last several decades. On behalf of the International Lymphoma Epidemiology Consortium (InterLymph) Pathology Working Group, we present a proposed nested classification of lymphoid neoplasms to facilitate the analysis of lymphoid neoplasm subtypes in epidemiologic research. The proposed classification is based on the World Health Organization classification of lymphoid neoplasms and the International Classification of Diseases-Oncology, Third Edition (ICD-O-3). We also provide a translation into the proposed classification from previous classifications, including the Working Formulation, Revised European-American Lymphoma (REAL) classification, and ICD-O-2. We recommend that epidemiologic studies include analyses by lymphoma subtype to the most detailed extent allowable by sample size. The standardization of groupings for epidemiologic research of lymphoma subtypes is essential for comparing subtype-specific reports in the literature, harmonizing cases within a single study diagnosed using different systems, as well as combining data from multiple studies for the purpose of pooled analysis or meta-analysis, and will probably prove to be critical for elucidating etiologies of the various lymphoid neoplasms.